Push button switches are well known in which a push button projects from the front of a housing, and a switch inside the housing is actuated by depressing the push button. The push botton can be illuminated from the rear by lamps mounted behind the face of the push button.
This type of push button switch has numerous avionics uses, such as in navigational systems generally, and more specifically in radar systems and airborne electronic systems controls. In many avionics uses, there is an urgent need to reduce the size and weight of these switches as much as possible. For example, in fighter planes the current cost of added weight is approximately $88,000.00 per pound, and size reduction carries a similar premium. The miniature size and intricate arrangement of component parts in such avionics switches require a switch assembly designed to ensure long-term reliability.
Such avionics uses also dictate the need to quickly and easily gain access either to the switch mechanism or to the lamps for maintenance or relamping purposes. The miniature size and intricate arrangement of the switch assembly can make relamping or maintenance difficult.
To permit the push button to be removed from its housing without tools of any sort, the push button may be secured to the rest of the switch mechanism by frictional engagement with a suitable detent mechanism which allows the push button to be withdrawn by pulling strongly on the projecting portion of the push button. After relamping or other maintenance is completed, the push button is replaced by pushing it back into position in the housing. There is a need to facilitate such removal of the push button, for relamping or other maintenance to the switch assembly, and proper replacement of the push button with a minimum of time or error.
Indicator lights also have numerous avionics uses requiring reduced size and weight, long term reliability and ease of maintenance and relamping.